diff --git a/src/Db/Core.php b/src/Db/Core.php
index 5f9314b..392649b 100644
--- a/src/Db/Core.php
+++ b/src/Db/Core.php
@@ -620,7 +620,7 @@ public function fetchAssoc()
 
         if (count($hidden)) {
             foreach ($hidden as $item) {
-                if (isset($result[$item])) {
+                if (array_key_exists($item, $result)) {
                     unset($result[$item]);
                 } elseif (strpos($item, '.') !== false) {
                     $hiddenEagerFields[] = explode('.', $item);
@@ -727,7 +727,7 @@ public function fetchAll($type = 'assoc')
 
             if (count($hidden)) {
                 foreach ($hidden as $item) {
-                    if (isset($result[$item])) {
+                    if (array_key_exists($item, $result)) {
                         unset($result[$item]);
                     } elseif (strpos($item, '.') !== false) {
                         $hiddenEagerFields[] = explode('.', $item);
diff --git a/tests/db.test.php b/tests/db.test.php
index a28b818..1f9f221 100644
--- a/tests/db.test.php
+++ b/tests/db.test.php
@@ -250,3 +250,25 @@
         ->and($db->select('users')->orderBy('name')->count())->toBe(3)
         ->and($db->select('users')->orderBy('name')->limit(2)->count())->toBe(2);
 });
+
+test('hidden removes fields whose value is null', function () {
+    // https://github.com/leafsphp/db/issues/42
+    $db = testDb();
+    $db->query('CREATE TABLE tokens (
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        email TEXT NOT NULL,
+        reset_token TEXT NULL
+    )')->execute();
+    $db->insert('tokens')->params(['email' => 'mika@leafphp.dev', 'reset_token' => null])->execute();
+    $db->insert('tokens')->params(['email' => 'jane@leafphp.dev', 'reset_token' => null])->execute();
+
+    $row = $db->select('tokens')->where('email', 'mika@leafphp.dev')->hidden('reset_token')->first();
+    expect($row)->not->toHaveKey('reset_token')
+        ->and($row)->toHaveKey('email');
+
+    $rows = $db->select('tokens')->hidden('reset_token')->all();
+    expect($rows)->toHaveCount(2);
+    foreach ($rows as $r) {
+        expect($r)->not->toHaveKey('reset_token');
+    }
+});